Many thermostatic switches are known which have contacts mounted on one or more flexible strips, with at least one of the flexible strips being formed of, or biased by, a bimetal material for movement subject to temperature variations. With such constructions, it is possible to provide relatively accurate electrical control responsive to temperature changes.
One particular type of thermostatic switch is the creep-action thermostatic switch. The creep-action is accomplished by the use of a bimetallic member, which, through expansion causes a pair of contacts to separate when a preset temperature is reached. Due to the creep-action, there is a gradual separation of the contacts, as the contact disposed at the end of the bimetallic member moves into or out of engagement with a mating contact. The contacts typically engage at the same contact point with the making and breaking of the contacts producing an arc as current begins to flow or is stopped. The continued proximity of the contacts after separation increases the propensity for arcing, producing a residue on the contact surfaces. Frequent cycles cause a residue build-up which increases the resistance between the contacts and affects switch operation.